Tulip contact is generally used in middle and/or high voltage switching devices. The contact fingers are essentially intended for rated electrical current disconnection operation and current transmission by providing a contact finger-trap which is connected to a mating contact.
U.S. Pat. No. 4,072,392A discloses a spring wire formed tulip contact which comprises cylindrical male contact 11 and female members 12, as shown in FIG. 1A. The female member 12 is formed by placing a number of spring wire fingers 13 around the outer circumference of a cylindrical stud member 14 in such a manner that the fingers 13 extend axially outward from the stud 14 to form a female contact sleeve 15. Each of the fingers 13 is bent axially inward with respect to the stud 14 in order that the internal diameter of the female contact sleeve 15 is shorter than the external diameter of the cylindrical male contact 11. The fingers 13 can electrically and mechanically contact with the cylindrical male contact 11. This tulip contact employs inexpensive spring wire which is readily available and free from defects. And the individual wire fingers may be formed into the desired shape by using a one-step automated form and cut-off machine. But this tulip contact does not have a large effective contact area.
EP0856860B1 discloses a tulip contact for a high voltage switching devices, as shown in FIG. 1B. The tulip contact 16 is designed to hold a mating contact 17 in the form of a pin, with contact fingers 18 arranged in a circular shape. A cylinder 19 is provided axially with slots being integrally formed on a circular ring 20. A ring is integrally formed on the end of the cylinder 19 opposite to the circular ring and its cross-sectional shape, together with the cylinder 19, is in the form of a golf club. The free axial end of the ring has a radial annular surface 21 on which a section 17 made of erosion resistant material is mounted. The internal diameter of the tulip contact 16 corresponding to the mating contact is shorter than the internal diameter of the section 17 made of erosion resistant material. This tulip contact has the disadvantage that its structure is not very firm.
US20070246444A1 discloses an electrical contact system for a switching device, as shown in FIG. 1C. The system has a contact 23 including a tulip-shaped contact unit, which is provided on a fixed plate 25. The plate 25 is connected to an axle tube 26 which is made of copper. The contact unit has contact fingers 24 with inner and outer surfaces. The surfaces fit into a counter contact 27 when a switching device is in a closed operating condition to form contacting surfaces for supplying current to the contact 27. The inner and outer surfaces of the contact fingers reduce the number of contact fingers 24, and improve the alignment tolerances. The fixed plate on which the tulip-shaped contact unit is provided is connected with the axle tube, thus reducing the contact transition resistance from the tulip-shaped contact unit to the axle tube.
In addition to above mentioned shortcomings of the traditional tulip contacts, all these tulip contacts do not possess such most important qualities as high electric conductivity, low heat generation and high heat ventilation.